1. Field of the Invention
The present invention relates generally to the area of x-ray imaging systems and devices used with such diagnostic x-ray systems. More specifically, the present invention relates to a C-arm x-ray imaging apparatus that incorporates new and improved mechanisms for adjustment and control of the C-arm.
2. Background of the Invention
It is frequently necessary to conduct an x-ray examination of a patient without repositioning the patient. To that end, mobile C-arm x-ray diagnostic equipment, such as that shown in FIG. 1, has been developed to meet this need. Such equipment is now well known in the medical and surgical arts. The C-arm machine is especially useful in that it is small enough and mobile enough to be present in an operating or exam situation without requiring the physician to repeatedly move or requiring the patient to change positions to obtain a suitable image.
C-arm imaging machines are well known and widely used in the medical arts. Examples of their uses include bone density measurement and fluoroscopic imaging during surgical procedures. The term xe2x80x9cC-armxe2x80x9d refers to the generally C-shaped member that has an x-ray source and an image receptor, or detector, mounted on opposing ends of the xe2x80x9cCxe2x80x9d such that x-rays emitted by the source are incident on and detected by the receptor. The source and the detector are positioned such that when, for example, a human extremity is interposed between the x-ray source and the image receptor and is thereby irradiated with x-rays, the receptor produces data representative of characteristics of the interposed extremity. The data produced is frequently displayed on a monitor and electronically saved.
The C-arm portion of the machine is normally mounted such that it is permitted two degrees of freedom. First, the C-arm track is slidably mounted to the support member so as to be movable in relation to the support member. This permits the x-ray source and image receptor to be moved rotatably about the arc of curvature of the track in the C-arm. The C-arm support member also permits rotation of the C-arm about its axis. Often the support member is referred to as the yoke. Mobile C-arms have a third degree of freedom in that they are free to move horizontally along the floor and a fourth in that the C-arm can be raised and lowered.
Obviously, a support structure that permits rotation and movement of such a C-arm must be properly counterbalanced and constructed to withstand large torsional, tensile and compressive stresses. It is also desirable to provide a support structure that is heavy enough and that has a center of gravity low enough to avoid tipping when the C-arm and Yoke are rotated or raised, which in some cases causes a dramatic shift in the center of mass of the machine.
Notwithstanding its size and mass, the C-arm x-ray machine must be delicately positioned in order to render the image or images as are desired or required by the physician. Unfortunately, the weight of the support structure can make it difficult to position the C-arm. Therfore, t is also desirable to balance the C-arm, x-ray source, x-ray detector and yoke so that relatively little physical effort is required to move the C-arm about the orbital rotation axis and the lateral rotation axis. One manner of accomplishing this is to design the C-arm such that its center of mass is as close as possible to the orbital and lateral rotation axes.
Some C-arm designs require a center of mass that is separate from the axis of rotation. In these unbalanced designs, the user must exert significant force to rotate the apparatus. This physical exertion generally detracts from other, more significant tasks a health care provider may be undertaking. Also, unbalanced designs can be dangerous to both the operator and the patient. For example, unbalanced C-arms require much more powerful braking systems. Without an adequate braking system, the C-arm could rotate downward and strike an individual.
What is needed is a C-arm x-ray machine that has a lower rotation axis such that the axis of rotation passes through the center of gravity of the yoke and the C-arm portion of the machine. What is also needed is such a machine whereby the overall length is reduced. What is also needed is such a machine whereby sag of the C-arm portion of the machine is compensated for. What is also needed is such a machine whereby miminal impact is effected on the existing support structures of the C-arm machine so that mainframe designs can continue to be utilized notwithstanding the aforementioned improvements.
Accordingly, it is an object of the present invention to provide a C-arm x-ray machine that is optimally balanced and requires little effort to rotate. It is yet another object of the present invention to provide such a device that requires relatively few parts and can be easily manufactured. It is also an object of this invention to reduce the overall length of the system. It is still another object of the present invention to provide such a machine whereby the rotation axis passes through the center of gravity of the yoke and the C-arm structure. It is yet another object of the present invention to reduce the overall length of the machine, reduce mass of the yoke and to compensate for sag of the C-arm portion of the machine. It is a further object of the present invention to provide such a machine whereby this alteration can be utilized with existing mainframes, or xe2x80x9cdoghousesxe2x80x9d of current design. It is yet another object of the present invention to accomplish all of this while providing an aesthetically pleasing and aseptic device.
The device of the present invention has achieved these objects. It provides for a C-arm x-ray apparatus having a support arm between the yoke and the cross arm that reduces the space used by the x-ray apparatus by taking advantage of the space that exists underneath the cross arm. This new support arm is also designed to align the axis of rotation of the C-arm with the C-arm""s center of gravity. The new support arm is also constructed so as to minimize mass and to compensate for C-arm sag by creating an angular presentation of the arm relative to the horizontal. Additional objects and advantages of the invention will be set forth in the description that follows. Other objects and advantages may be learned by practice of the invention.